Perforating gun assemblies are used in many oilfield or gas well completions. In particular, the assemblies are used to generate holes in steel casing pipe/tubing and/or cement lining in a wellbore to gain access to the oil and/or gas deposit formation. In order to maximize extraction of the oil/gas deposits, various perforating gun systems are employed. These assemblies are usually elongated and frequently cylindrical, and include a detonating cord arranged within the interior of the assembly and connected to shaped charge perforators (or shaped charges) disposed therein.
The type of perforating gun assembly employed may depend on various factors, such as the conditions in the formation or restrictions in the wellbore. For instance, a hollow-carrier perforating gun system having a tube for carrying the shaped charges may be selected to help protect the shaped charges from wellbore fluids and pressure (the wellbore environment). An alternative perforating gun system often used is an exposed or encapsulated perforating gun system. This system may allow for the delivery of larger sized shaped charges than those of the same outer diameter sized hollow-carrier gun system. The exposed perforating gun system typically includes a carrier strip upon which shaped charges are mounted. Because these shaped charges are not contained within a hollow tube, as those of a hollow-carrier perforating gun system, the shaped charges are individually capsuled.
Typically, shaped charges are configured to focus ballistic energy onto a target to initiate production flow. Shaped charge design selection is also used to predict/simulate the flow of the oil and/or gas from the formation. The configuration of shaped charges may include conical or round aspects having an initiation point formed in a metal case, which contains an explosive material, with or without a liner therein, and that produces a perforating jet upon initiation. It should be recognized that the case or housing of the shaped charge is distinguished from the casing of the wellbore, which is placed in the wellbore after the drilling process and may be cemented in place in order to stabilize the borehole and isolate formation intervals prior to perforating the surrounding formations.
Current perforating gun systems are mechanically connected via tandem sub assemblies. For wireline conveyance and selective perforating, the perforating gun is also electrically connected to an adjacent perforating gun by a bulkhead, which is included in the tandem sub. The bulkhead typically provides pressure isolation and includes an electric feedthrough pin. Each perforating gun may include multiple wires, such as feed-through or grounding wires as well as a detonating cord, which typically run parallel to each other through the length of the perforating gun. The feed-through wire is typically configured to electrically connect a perforating gun to an adjacent perforating gun, and the detonating cord is typically configured to initiate shaped charges disposed in each perforating gun. Further description of such perforating guns may be found in commonly-assigned U.S. Pat. Nos. 9,605,937, 9,581,422, 9,494,021, and 9,702,680, each of which are incorporated herein by reference in their entireties. Other perforating gun systems may utilize charge tubes/charge cartridges as a reduction option for the feed-through wire or separate electronic switches in the gun (sometimes externally connected to the detonator) that allows you to switch between different gun assemblies. Such perforating guns are described in U.S. Pat. Nos. 8,689,868, 8,884,778, 9,080,433, and 9,689,223. The use of multiple wires often requires additional assembly steps and time, which may result in increased assembly costs.
In view of the disadvantages associated with currently available perforating gun assemblies there is a need for a device that reduces assembly steps and time and improves safety and reliability of perforating gun assemblies. There is a further need for a perforating gun having simplified wiring, which may reduce human error in assembling perforating gun systems. Further, this results in a need for a detonating cord that relays/transfers electrical signals along a length of a perforating gun, without requiring additional wires, and without the need to isolate conductive elements.